This invention relates to screw conveyors, and more particularly, to couplings which connect screw conveyor sections.
Screw conveyors or auger conveyors are used to convey rice, grain and other raw food products and bulk material. Auger conveyors are used extensively to move grain horizontally. In a milling facility, auger conveyors can be used to unload raw product from incoming trucks and railcars, to unload and load storage silos, to feed milling and separation equipment, and to load processed and finished product.
Screw conveyors typically include a helical screw within a housing or trough. In operation, screw conveyors rotate about their longitudinal axis to convey material along the length of the helical screw. Screw conveyors are usually fabricated of metal and can be of fixed length and size. Screw conveyors have also been constructed of modular or segmented sections which can be assembled into a complete conveyor of a preferred length. Modular sections are useful to lengthen or shorten a conveyor so as to better fit the distance between pickup and delivery of the material being conveyed.
In the past, couplings for connecting together sections of a screw conveyor included a single, solid cylindrical shaft. The ends of the couplings were secured at each end by bolts that extend through the shafts and the couplings. In order to replace a worn coupling, the sections extending from that coupling to one of the ends of the conveyor had to be loosened and moved axially. This is very awkward and cumbersome. In a further effort to solve the problems, shafts and the couplings have both been modified in various ways to permit removal of the couplings without moving the shafts of the conveyor sections. This technique is very expensive.
The present widely used method of coupling and assembling sections of auger conveyors utilizes bolts and nuts. This causes many problems. The coupling bolts are constantly in shear and often split, chip, shear, wear through or otherwise fail from torsion, torque, tension, compression, shear or other dynamic forces causing pieces of the bolts or nuts to be conveyed and carried forward with grain or other conveyed food products. Metal chips, slivers and pieces of bolts and nuts contaminate food products making it unsafe for human consumption. Furthermore, pieces of coupling bolts and nuts which are conveyed into processing equipment can cause costly damage and extensive repair. In the event, all the bolts in a coupling fail, the coupling will open, the conveyor sections will separate, and production will cease as product can no longer be conveyed by a separated conveyor.
Even if coupling bolts are consistently maintained, i.e., changed prior to failure, wear becomes a factor of failure in the coupling shaft and/or the hollow pipe shaft of the auger itself. Constant torquing of the coupling bolt against the coupling bolt hole can cause the bolt hole to become increasingly enlarged and weaken the coupling shaft to cause absolute failure, i.e., shearing off of the bolted pieces. The auger conveyor then fails to transport product, causing immediate product backup upstream. If the coupling hole wear is seen at the hollow auger shaft, the section of auger in question should be replaced.
Besides bolts, other techniques and fastener arrangements have been suggested to connect screw conveyor sections, such as locking pins and tension springs, but they have not been generally successful.
It is, therefore, desirable to provide an improved coupling and process to connect screw conveyor sections, which overcome most, if not all of the preceding problems.